The present invention relates to a noise reduction structure for a cab of a working vehicle such as a hydraulic shovel.
A hydraulic shovel 1 being a working vehicle shown in FlG. 9 has a base carrier 2 and a revolving superstructure 4 rotatably mounted on the base carrier 2 (for example, Japanese Patent Laid-open No. 8-81976). The revolving superstructure 4 has a frame 12 at the lower part thereof. A working machine 6 is provided in the almost center of the front portion of the frame 12, a cab 10 is provided on either left or right side of the front portion thereof, and an engine room 8, which is covered with a cover and houses power plants such as an engine and a hydraulic pump not illustrated therein, is provided at the rear portion thereof.
In FIG. 10, a cab 10c is mounted on a top face of a frame 12c via vibration isolating members (not illustrated), with predetermined distance being spaced from the top face of the frame 12c and the front face of the engine room 8. The frame 12c is formed to be a frame shape so as to cover the entire perimeter of the side face of the lower part of the cab 10c. A cover 14 for protecting the bottom face of the cab 10c from earth and stones, and muddy water is mounted on the bottom face of the frame 12c. Further, a lever stand 26 mounted with a working machine lever 30 for operating the working machine 6, a console 28 mounted with a control unit 50, and a traveling lever 40 for performing a traveling operation, are mounted on the floor 11c of the cab 10c. 
Pilot valves 31 and 41 for converting pilot oil pressure from a pilot pump (not illustrated) into command pilot oil pressure corresponding to a lever manipulated variable are respectively provided at the lower portion of the working machine lever 30 and the traveling lever 40. A plurality of hydraulic hoses 32 and 42, which are connected to hydraulic devices such as a pilot pump, an operating valve and a tank not illustrated, are connected to the pilot valves 31 and 41. It should be noted that control cables 32 and 42 are used instead of the hydraulic hoses 32 and 42 in some examples. A wiring harness 52 for exchanging signals with control devices, detectors and the like not illustrated is connected to the control unit 50.
The traveling lever 40 is mounted on the top face of the floor 11c, and thus the pilot valve 41 of the traveling lever 40 is mounted so as to be protruded below the floor 11c from a through-hole 45 of the floor 11c. The hydraulic hose 42 connected to the pilot valve 41 at a portion below the floor 11c extends under the floor 11c to be connected to the hydraulic devices behind the cab 10c. 
The working machine lever 30 is mounted on the lever stand 26. Since the pilot valve 31 of the working machine lever 30 is located above the floor 11c, the hydraulic hose 32 connected thereto extneds under the floor 11c via a gromet 37 attached to a through-hole 35 of the floor 11c from above the floor 11c to be connected to the hydraulic devices behind the cab 10c. As shown in FIG. 11A and FIG. 11B, the gromet 37 is in an almost oval shape having a thin center portion 37a in the center portion and a thick perimeter portion 37b in the perimeter portion, and is made by rubber molding. A plurality of holes 37c having almost the same diameter as an outer diameter of the hydraulic hose 32 are provide at predetermined intervals in the center portion 37c, and slits 37d connecting the adjacent two holes 37c and 37c with each other arc provided for the purpose of passing a mouth piece of the hydraulic hose 32 through. A groove 37e with a predetermined depth with almost the same width as the thickness of the floor 11c is provided on an outer perimeter surface of the perimeter portion 37b. 
Further, the working machine lever 30 has a structure which is capable of sliding in a longitudinal direction of the vehicle in accordance with a physique and preference of an operator, and in accordance with an operational situation such as an operation of digging a deep hole in which a forward tilting posture is required. The wiring harness 52 from the control unit 50 extends under the floor 11c via the through-hole not illustrated of the floor 11c from above the floor 11c to be connected to the control devices and detectors outside the cab 10c. 
When an operator starts the engine and manipulates the working machine lever 30 or the traveling lever 40 to operate the hydraulic shovel 1 for operation, noises are generated from the power plants such as the engine, the hydraulic pump, and the like. The noises generated propagate into the cab 10c, and they propagate in such a manner as to especially concentrate on a rear face of the cab 10c, which is near the noise sources. Conventionally, in order to reduce noise, a structure which increases sound-insulating effectiveness, for example, by reducing a gap by means of a gromet, or providing sound-insulating members and the like is adopted in the cab 10c. However, recently, a demand for increased riding comfort and sound-insulating effectiveness in the cab 10c grows. Accordingly, further noise reduction inside the cab 10c is required.
Further, by sliding movement of the working machine lever 30, the hydraulic hose 32 moves together with the pilot valve 31. In this situation, due to the sliding amount, the rigidity and the thickness of the hydraulic hose 32, as shown in FIG. 11C, the hose 32 is on the skew at the gromet 37 section, which together with the existence of the slit 37d, causes a gap due to twisting. Further, since the hydraulic hose 32 is not fixed in the vicinity of the gromet 37 in order to absorb play caused by the sliding movement, a gap caused by the twist sometimes remains even if the sliding movement is stopped to return to the original position. For this reason, in the through-hole 35, a degree of sound-insulating effectiveness of the gromet 37 is extremely reduced. In addition, in the through-hole 45 section to which the traveling lever 40 is mounted, a secure sound-insulating structure sometimes cannot be achieved for the reason of design.
Since the cab 10c is mounted to be spaced from the frame 12c, due to the noise entering from a gap between the cab 10c and the frame 12c, a level of noise below the floor 11c is higher. Consequently, the noise below the floor 11c enters the inside of the cab 10c through the through-holes 35 and 45 where sound insulation is incomplete, which poses the big barrier to the noise reduction inside the cab 10c. 
The present invention is made in view of the above disadvantages, and its object is to provide a noise reduction structure for a cab of a working vehicle, by which a higher level of noise reduction effectiveness can be surely obtained, in a working vehicle such as a hydraulic shovel. Another object is to provide the noise reduction structure for the cab which prevents noise from entering from through-holes provided in a floor and a wall surface of the cab for providing hydraulic hoses and a wiring harness, and has a higher level of noise reduction effectiveness, in the working vehicle such as a hydraulic shovel.
In order to attain the above object, a first aspect of a noise reduction structure for a cab of a working vehicle according to the present invention is in a noise reduction structure for a cab of a working vehicle, characterized in that
a sound-insulating chamber adjacent to a cab is provided at a position of at least one of the following: under a floor of the cab, behind a rear wall of the cab, and at a side of a side wall of the cab.
According to the above configuration, out of the paths through which noises propagate into the cab of the working vehicle such as a hydraulic shovel, the noises propagating into the cab from the rear wall of the cab, the floor of the cab, and the side wall of the cab, which are near the noise sources and the main causes of noise, can be reduced by being passed through the sound-insulating chambers. Hence, working environment for an operator can be improved, and working efficiency can be improved. In addition, the sound-insulating chambers can be respectively realized with a simple structure utilizing the existing members such as the floor and the frame; the rear wall of the cab and the engine room; and the side wall of the cab and the boom supporting member.
A second aspect of a noise reduction structure for a cab of a working vehicle according to the present invention is in a noise reduction structure for a cab of a working vehicle in which at least one of hydraulic hoses, wiring harness and control cables is provided to extend from an inside of the cab to an outside thereof via through-holes provided in the cab, and noise entering via the through-holes is reduced, characterized by including:
a sound-insulating chamber which is provided adjacent to the cab, communicated with the cab via the through-holes, and sound-insulated from the outside, and characterized in that
at least one of the hydraulic hoses; the wiring harness; and the control cables is provided to extend from the inside of the cab to the outside thereof via the through-holes and the sound-insulating chamber.
According to the above configuration, in the working vehicle such as a hydraulic shovel, the hydraulic hoses, the wire harness and the like are provided to extend from the inside of the cab to the outside thereof via the through-holes and the sound-insulating chambers. In this situation, even when sound insulation is difficult at the through-hole section, and even when sound insulation is difficult at the through-hole section at which the manipulating member is directly mounted on the floor, sound insulation is achieved at the exit portion to the outside from the sound-insulating chamber. As a result, noise from the outside is reduced in the sound-insulating chambers, and thereby the noise entering the inside of the cab from the sound-insulating chambers through the through-holes is reduced. Thus, the noise reduction inside the cab is made possible, the working environment for an operator can be improved, and working efficiency can be improved.
Further, with the through-hole being provided in the floor of the cab, the sound-insulating chamber may be configured to have the floor of the cab, the frame on which surface the cab is mounted, and the sound-insulating member for padding a gap between the cab and the frame. The sound-insulating chamber has a simple configuration in which the members such as the floor and the frame conventionally used are partially modified as necessary and the sound-insulating member is added. As a result, the noise reduction inside the cab is made possible with a simple structure, and the working environment for an operator is improved, thus making it possible to improve working efficiency.